The main functions of this core are the detection and functional characterization of p53 mutation in sarcoma kindreds. These analyses are essential for the aims of projects 1, 4, and 5. Dr. Strong (project 1) uses the data obtained from this core to characterize excess cancer risk in kindreds of childhood sarcoma patients, to assess the relative contribution of p53 germline mutations to childhood sarcoma, and to identify paternal origin of de novo mutations. Additionally, since our discovery of non-p53 cancer prone kindreds, she will characterize cancer risk in these kindreds as well. Her ability to do these analyses is dependents of establishing which individuals carry p53 germline mutations. The data obtained by this core are also essential for Dr. Lozano's aim (project 4) to map the locus or loci responsible for cancer predisposition in non p53 cancer prone kindreds since the identification of additional families and individuals strengthens the power needed for linkage analysis. To determiner where there is a distinct quantitative microsatellite instability phenotype associated with p53 mutations (project 5, Dr. Siciliano), it is clearly essential to identify the patients with germline p53 mutations. The specific aims of this core are: 1) to sequence the p53 coding exons and flanking splice junctions from the probands of the soft tissue sarcoma and osteosarcoma cohorts to identify the presence or absence of germline p53 mutations 2) to examine those samples in which a p53 mutation is not identified by (1) above by southern analysis to exclude possible gross deletions of one of the p53 alleles 3) to examine LOH in tumors and immortalized fibroblasts from LFS patients with and without p53 mutations 4) to develop SSCP and ASO methods to screen family members upon identification of the specific p53 mutation and to screen o6ther known tumor suppressor genes in non p53 kindreds 5) to perform functional analyses of p53 mutations using the yeast functional assay and transient transfection experiments in tissue culture cells to document functional differences between mutations. The function of this core will eventually evolve to include mutational analyses of the other gene or genes that predispose to cancer (see project 4 and core E).